1. Field of the Invention
The present invention relates to locomotive braking systems and, more particularly, to a system and method for incrementally reducing brake pipe pressure.
2. Description of the Related Art
Locomotive operators using pneumatic or electro-pneumatic braking systems are often required to make minor reductions in brake pipe pressure beyond the minimum braking level when grade braking or in other situations. Brake control levers positioned on a locomotive mounted brake controller are used as the man machine interface for brake pipe control. These levers typically have set positions for a defined reduction of equalizing reservoir (ER) pressure, which is the pilot pressure for the brake pipe relay and thus provides the target level for the brake pipe (BP) pressure. For example, the handle position typically labelled ‘minimum’ allows for the minimum amount of brake which can be applied, while the position referred to as ‘full service’ provides for a normal, full brake application.
While it is easy for an operator to get the brake pipe reduction requested at the ‘set’ positions, such as ‘minimum’ or ‘full service’, often the operator would like to have a reduction of brake pipe (BP) pressure just slightly greater than afforded by the ‘minimum’ position to operate the train in certain conditions. In these cases, the operator often must carefully manipulate the lever beyond the ‘minimum’ position toward the ‘full service’ position with caution so as not to over-brake the train. While control levers are good at giving the operator quick intuitive control of the brake level, they do not allow an operator to control the brake pipe (BP) pressure between the preconfigured ‘set’ positions as precisely as they desire in some situations. Another issue with conventional braking systems is that the locomotive operators making reductions in brake pipe pressure must often prevent the locomotives brakes from applying by using a bail off feature due to operating rules or the conditions of train control. In these cases, the operator must use both hands to apply the brakes. These same issues exist in electronically controlled pneumatic (ECP) brake systems.